Department of Cell Biology and Anatomy Miller School of Medicine, University of Miami, Miami, Florida 33136, USA.
J Cell Biochem. 2010 Aug 15;110(6):1365-75. doi: 10.1002/jcb.22653.
Non-muscle myosin II (NM II) helps mediate survival and apoptosis in response to TNF-alpha (TNF), however, NM II's mechanism of action in these processes is not fully understood. NM II isoforms are involved in a variety of cellular processes and differences in their enzyme kinetics, localization, and activation allow NM II isoforms to have distinct functions within the same cell. The present study focused on isoform specific functions of NM IIA and IIB in mediating TNF induced apoptosis. Results show that siRNA knockdown of NM IIB, but not NM IIA, impaired caspase cleavage and nuclear condensation in response to TNF. NM II's function in promoting cell death signaling appears to be independent of actomyosin contractility (AMC) since treatment of cells with blebbistatin or cytochalasin D failed to inhibit TNF induced caspase cleavage. Immunoprecipitation studies revealed associations of NM IIB with clathrin, FADD, and caspase 8 in response to TNF suggesting a role for NM IIB in TNFR1 endocytosis and the formation of the death inducing signaling complex (DISC). These findings suggest that NM IIB promotes TNF cell death signaling in a manner independent of its force generating property.
非肌肉肌球蛋白 II（NM II）有助于介导对 TNF-α（TNF）的存活和凋亡反应，然而，NM II 在这些过程中的作用机制尚不完全清楚。NM II 同工型参与多种细胞过程，其酶动力学、定位和激活的差异使 NM II 同工型在同一细胞中具有不同的功能。本研究集中于 NM IIA 和 IIB 在介导 TNF 诱导的细胞凋亡中的同工型特异性功能。结果表明，siRNA 敲低 NM IIB，但不影响 NM IIA，可损害 TNF 诱导的半胱天冬酶切割和核浓缩。NM II 在促进细胞死亡信号转导中的作用似乎独立于肌动球蛋白收缩性（AMC），因为用 blebbistatin 或细胞松弛素 D 处理细胞不能抑制 TNF 诱导的半胱天冬酶切割。免疫沉淀研究表明，NM IIB 与 TNF 反应中的网格蛋白、FADD 和 caspase 8 相关，提示 NM IIB 在 TNFR1 内吞作用和形成死亡诱导信号复合物（DISC）中发挥作用。这些发现表明，NM IIB 以独立于其产生力的特性促进 TNF 细胞死亡信号转导。
